This invention is related to an industrial pneumatic cylinder having an internal, liquid dampening means for cushioning the end of the (cylinder) stroke.
Industrial pneumatic cylinders commonly use some means for cushioning the cylinder at the end of the piston stroke. Conventional pneumatic cylinders have an internal pneumatic device intended to cushion the end of the piston stroke; however, such devices are only satisfactory in a controlled atmosphere, that is, where temperature and humidity is controlled. Certain industries, such as the medical industry, and some printing industries control the air for other reasons. Such cylinder cushions appear to be satisfactory in such an environment. However, in a general industrial atmosphere, pneumatic cylinders using air for cushioning the shock at the end of the stroke are generally unsatisfactory. Consequently, the practice is to use an external hydraulic shock absorber to cushion the end of the stroke. Such an arrangement is bulky and not always reliable.
The broad purpose of the present invention is to provide a pneumatic cylinder having an internal hydraulic shock absorber, which cushions the end of the stroke.
Typically, a pneumatic cylinder has an internal piston mounted on a rod in a barrel that provides a pressure chamber. As the piston rod is reciprocated, the piston moves toward either the head or the cap, its motion being controlled by regulating either the pressurized incoming air, or the air exhaust. It is important in some applications to incorporate a retarding or cushioning device at either one or both ends of the stroke.
In the preferred embodiment of the invention, a pneumatic piston carries a pair of open cylinders, one facing the cylinder head, the other facing the cylinder cap. Two floating shock pistons are slidably mounted on the piston rod on opposite sides of the pneumatic piston and slide in the open cylinders to form a pair of hydraulic (cushioning) chambers. As the pneumatic piston approaches one end of its stroke, the shock piston between the end of the pneumatic chamber and the pneumatic piston causes oil in one of the cushioning chambers to pass through a metering passage toward the cushioning chamber on the opposite end of the pneumatic piston. The size of the metering passage controls the final deceleration of the pneumatic piston.
When the piston moves in the opposite direction, the other shock piston functions in a similar way. Thus, the end of each stroke of the pneumatic piston is controlled by an internal hydraulic shock absorber. Several structures are disclosed for metering the oil passing between the cushioning chambers.
Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description.